Effects of paracrine factors on CD24 expression and neural differentiation of male germline stem cells

Epigenetic inheritance of acquired traits via stem cells dedifferentiation/differentiation or transdifferentiation cycles

Inheritance of acquired characteristics is the once widely accepted idea that multiple modifications acquired by an organism during its life, can be inherited by the offspring. This belief is at least as old as Hippocrates and became popular in early 19th century, leading Lamarck to suggest his theory of evolution. Charles Darwin, along with other thinkers of the time attempted to explain the mechanism of acquired traits' inheritance by proposing the theory of pangenesis. While later this and similar theories were rejected because of the lack of hard evidence, the studies aimed at revealing the mechanism by which somatic information can be passed to germ cells have continued up to the present. In this paper, we present a new theory and provide supporting literature to explain this phenomenon. We hypothesize existence of pluripotent adult stem cells that can serve as collectors and carriers of new epigenetic traits by entering different developmentally active organ/tissue compartments through blood circulation and acquiring new epigenetic marks though cycles of differentiation/dedifferentiation or transdifferentiation. During gametogenesis, these epigenetically modified cells are attracted by gonads, transdifferentiate into germ cells, and pass the acquired epigenetic modifications collected from the entire body's somatic cells to the offspring.

Apoptosis in Postmortal Tissues of Goat Spinal Cords and Survival of Resident Neural Progenitors

Growing demand for therapeutic tissue repair recurrently focusses scientists' attention on critical assessment of postmortal collection of live cells, especially stem cells. Our study aimed to assess the survival of neuronal progenitors in postmortal spinal cord and their differentiation potential. Postmortal samples of spinal cords were obtained from human-sized animals (goats) at 6, 12, 24, 36, and 54 h after slaughter. Samples were studied by immunohistology, differentiation assay, Western blot and flow cytometry for the presence and location of GD2-positive neural progenitors and their susceptibility to cell death. TUNEL staining of the goat spinal cord samples over 6-54 h postmortem revealed no difference in the number of positive cells per cross-section. Many TUNEL-positive cells were located in the gray commissure around the central canal of the spinal cord; no increase in TUNEL-positive cells was recorded in either posterior or anterior horns of the gray matter where many GD2-positive neural progenitors can be found. The active caspase 3 amount as measured by Western blot at the same intervals was moderately increasing over time. Neuronal cells were enriched by magnetic separation with antibodies against CD24; among them, the GD2-positive neural progenitor subpopulation did not overlap with apoptotic cells having high pan-caspase activity. Apoptotic cell death events are relatively rare in postmortal spinal cords and are not increased in areas of the neural progenitor cell's location, within measured postmortal intervals, or among the CD24/GD2-positive cells. Data from our study suggest postmortal spinal cords as a valuable source for harvesting highly viable allogenic neural progenitor cells.

The Impact of Hormesis, Neuronal Stress Response, and Reproduction, upon Clinical Aging: A Narrative Review

INTRODUCTION

The primary objective of researchers in the biology of aging is to gain a comprehensive understanding of the aging process while developing practical solutions that can enhance the quality of life for older individuals. This involves a continuous effort to bridge the gap between fundamental biological research and its real-world applications.

PURPOSE

In this narrative review, we attempt to link research findings concerning the hormetic relationship between neurons and germ cells, and translate these findings into clinically relevant concepts.

METHODS

We conducted a literature search using PubMed, Embase, PLOS, Digital Commons Network, Google Scholar and Cochrane Library from 2000 to 2023, analyzing studies dealing with the relationship between hormetic, cognitive, and reproductive aspects of human aging.

RESULTS

The process of hormesis serves as a bridge between the biology of neuron-germ cell interactions on one hand, and the clinical relevance of these interactions on the other. Details concerning these processes are discussed here, emphasizing new research which strengthens the overall concept.

CONCLUSIONS

This review presents a scientifically and clinically relevant argument, claiming that maintaining a cognitively active lifestyle may decrease age-related degeneration, and improve overall health in aging. This is a totally novel approach which reflects current developments in several relevant aspects of our biology, technology, and society.

The signal transducer CD24 suppresses the germ cell program and promotes an ectodermal rather than mesodermal cell fate in embryonal carcinomas

Testicular germ cell tumors (GCTs) are stratified into seminomas and nonseminomas. Seminomas share many histological and molecular features with primordial germ cells, whereas the nonseminoma stem cell population-embryonal carcinoma (EC)-is pluripotent and thus able to differentiate into cells of all three germ layers (teratomas). Furthermore, ECs are capable of differentiating into extra-embryonic lineages (yolk sac tumors, choriocarcinomas). In this study, we deciphered the molecular and (epi)genetic mechanisms regulating expression of CD24, a highly glycosylated signaling molecule upregulated in many cancers. CD24 is overexpressed in ECs compared with other GCT entities and can be associated with an undifferentiated pluripotent cell fate. We demonstrate that CD24 can be transactivated by the pluripotency factor SOX2, which binds in proximity to the CD24 promoter. In GCTs, CD24 expression is controlled by epigenetic mechanisms, that is, histone acetylation, since CD24 can be induced by the application histone deacetylase inhibitors. Vice versa, CD24 expression is downregulated upon inhibition of histone methyltransferases, E3 ubiquitin ligases, or bromodomain (BRD) proteins. Additionally, three-dimensional (3D) co-cultivation of EC cells with microenvironmental cells, such as fibroblasts, and endothelial or immune cells, reduced CD24 expression, suggesting that crosstalk with the somatic microenvironment influences CD24 expression. In a CRISPR/Cas9 deficiency model, we demonstrate that CD24 fulfills a bivalent role in differentiation via regulation of homeobox, and phospho- and glycoproteins; that is, it is involved in suppressing the germ cell/spermatogenesis program and mesodermal/endodermal differentiation, while poising the cells for ectodermal differentiation. Finally, blocking CD24 by a monoclonal antibody enhanced sensitivity toward cisplatin in EC cells, including cisplatin-resistant subclones, highlighting CD24 as a putative target in combination with cisplatin.

Deciphering the Nature of Trp73 Isoforms in Mouse Embryonic Stem Cell Models: Generation of Isoform-Specific Deficient Cell Lines Using the CRISPR/Cas9 Gene Editing System

Simple Summary

The Trp73 gene is involved in the regulation of multiple biological processes such as response to stress, differentiation and tissue architecture. This gene gives rise to structurally different N and C-terminal isoforms which lead to differences in its biological activity in a cell type dependent manner. However, there is a current lack of physiological models to study these isoforms. The aim of this study was to generate specific p73-isoform-deficient mouse embryonic stem cell lines using the CRISPR/Cas9 system. Their special features, self-renewal and pluripotency, make embryonic stem cells a useful research tool that allows the generation of cells from any of the three germ layers carrying specific inactivation of p73-isoforms. Characterization of the generated cell lines indicates that while the individual elimination of TA- or DN-p73 isoform is compatible with pluripotency, it results in alterations of the transcriptional profiles and the pluripotent state of the embryonic stem cells in an isoform-specific manner.

Abstract

The p53 family has been widely studied for its role in various physiological and pathological processes. Imbalance of p53 family proteins may contribute to developmental abnormalities and pathologies in humans. This family exerts its functions through a profusion of isoforms that are generated by different promoter usage and alternative splicing in a cell type dependent manner. In particular, the Trp73 gene gives rise to TA and DN-p73 isoforms that confer p73 a dual nature. The biological relevance of p73 does not only rely on its tumor suppression effects, but on its pivotal role in several developmental processes. Therefore, the generation of cellular models that allow the study of the individual isoforms in a physiological context is of great biomedical relevance. We generated specific TA and DN-p73-deficient mouse embryonic stem cell lines using the CRISPR/Cas9 gene editing system and validated them as physiological bona fide p73-isoform knockout models. Global gene expression analysis revealed isoform-specific alterations of distinctive transcriptional networks. Elimination of TA or DN-p73 is compatible with pluripotency but prompts naïve pluripotent stem cell transition into the primed state, compromising adequate lineage differentiation, thus suggesting that differential expression of p73 isoforms acts as a rheostat during early cell fate determination.

Application of microfluidic systems for neural differentiation of cells

Neural differentiation of stem cells is an important issue in development of central nervous system. Different methods such as chemical stimulation with small molecules, scaffolds, and microRNA can be used for inducing the differentiation of neural stem cells. However, microfluidic systems with the potential to induce neuronal differentiation have established their reputation in the field of regenerative medicine. Organization of microfluidic system represents a novel model that mimic the physiologic microenvironment of cells among other two and three dimensional cell culture systems. Microfluidic system has patterned and well-organized structure that can be combined with other differentiation techniques to provide optimal conditions for neuronal differentiation of stem cells. In this review, different methods for effective differentiation of stem cells to neuronal cells are summarized. The efficacy of microfluidic systems in promoting neuronal differentiation is also addressed.

Generation of functional dopaminergic neurons from human spermatogonial stem cells to rescue parkinsonian phenotypes

Background

Recent progress in the induced generation of dopaminergic (DA) neurons from different types of stem cells or reprogrammed somatic cells holds tremendous potential for the treatment of Parkinson’s disease (PD). However, the lack of a reliable source for cell replacement therapy remains a major limitation in the treatment of human neurological disorders. Additionally, the current protocols for in vitro differentiation or cell reprogramming to generate human DA neurons are laborious, time-consuming, and expensive, and efficient conversion of human spermatogonial stem cells (hSSCs) to functional DA neurons has not yet been achieved.

Methods

Primary hSSCs from testicular tissues of patients were exposed to an improved induction system, which consisted mainly of olfactory ensheathing cell conditioned culture medium (OECCM) and a set of defined cell-extrinsic factors and small molecules. Morphological changes were assessed, along with the expression of various DA neuron phenotypic markers (e.g., Tuj-1, TH, Nurr1, DAT) and several critical pro-DA neurogenesis effectors (e.g., EN-1, Pitx3, Foxa2, Lmx1a, Lmx1b, and OTX2). In addition, transcriptome analysis was used to further evaluate the genetic similarity between the artificially differentiated DA neurons and genuine ones. Concomitantly, the functional properties of converted DA neurons including synapse formation, dopamine release, electrophysiological activity, and neuron-specific Ca²⁺ signaling images were determined. Finally, hSSCs in the early stage of induction were evaluated for survival, differentiation, migration, tumorigenicity in the mouse striatum, and improvement of functional deficits in MPTP-induced PD animals.

Results

The hSSC-derived neurons not only acquired neuronal morphological features but also expressed various phenotypic genes and protein characteristic of DA neurons and several effectors critical for pro-DA neurogenesis. Strikingly, as the period of induction was prolonged, expression of the critical molecules for DA neuron epigenetic status gradually increased while hSSC-specific markers sharply decreased. After 3 weeks of induction, the transdifferentiation efficiency reached 21%. In addition, hierarchical clustering analysis showed that the differentiated DA neurons closely resembled genuine ones. Furthermore, the hSSC-derived neurons gained sophisticated functional properties of wild-type DA neurons, and pro-induced hSSCs efficiently survived, migrated, and differentiated into DA neurons without tumorigenesis after transplantation into mouse striatum, leading to improvement of functional deficits in PD animals.

Conclusions

The results showed that, using the present improved straightforward approach, hSSCs could acquire DA neuron morphological features and functional properties and rescue parkinsonian phenotypes. Our strategy for the conversion of hSSCs into DA neurons is very efficient and thus may provide an alternative approach suitable for clinical cell therapy to treat neurodegenerative diseases including PD.

Nanos2 promotes differentiation of chicken (Gallus gallus) embryonic stem cells to male germ cells

Nanos2 is an evolutionarily conserved RNA-binding protein containing 2 CCHC-type zinc finger motives. Here, we report that Nanos2 is strongly expressed in the testis compared to other tissues in chicken (Gallus gallus). Overexpression and knockout plasmid vectors were constructed, and in-vitro Cas9/gRNA digestion and T7 endonuclease I (T7E1) assay indicated that Nanos2-g1 possessed the highest knockout activity. In vitro and in vivo, Nanos2 overexpression accelerated the production of embryoid bodies (EBs) and SSC-like cells and promoted cvh, c-kit, and integrin α6 expression. Immunofluorescence staining, periodic acid schiff (PAS) and flow cytometry (FCM) assay showed that primordial germ cells (PGCs) and spermatogonial stem cells (SSCs) formation were significantly promoted. On the contrary, Nanos2 knockout delayed the production of EBs and SSC-like cells and correspondingly reduced cvh, c-kit, and integrin α6 expression. Simultaneously, the quantity of PGCs and SSCs was blocked. Collectively, these results uncovered a novel function of Nanos2 involved in chicken male germ cell differentiation, where it acts as a facilitator.

The Effect of Traditional Chinese Medicine on Neural Stem Cell Proliferation and Differentiation

Neural stem cells (NSCs) are special types of cells with the potential for self-renewal and multi-directional differentiation. NSCs are regulated by multiple pathways and pathway related transcription factors during the process of proliferation and differentiation. Numerous studies have shown that the compound medicinal preparations, single herbs, and herb extracts in traditional Chinese medicine (TCM) have specific roles in regulating the proliferation and differentiation of NSCs. In this study, we investigate the markers of NSCs in various stages of differentiation, the related pathways regulating the proliferation and differentiation, and the corresponding transcription factors in the pathways. We also review the influence of TCM on NSC proliferation and differentiation, to facilitate the development of TCM in neural regeneration and neurodegenerative diseases.

Optimal concentration and time window for proliferation and differentiation of neural stem cells from embryonic cerebral cortex: 5% oxygen preconditioning for 72 hours

Hypoxia promotes proliferation and differentiation of neural stem cells from embryonic day 12 rat brain tissue, but the concentration and time of hypoxic preconditioning are controversial. To address this, we cultured neural stem cells isolated from embryonic day 14 rat cerebral cortex in 5% and 10% oxygen in vitro. MTT assay, neurosphere number, and immunofluorescent staining found that 5% or 10% oxygen preconditioning for 72 hours improved neural stem cell viability and proliferation. With prolonged hypoxic duration (120 hours), the proportion of apoptotic cells increased. Thus, 5% oxygen preconditioning for 72 hours promotes neural stem cell proliferation and neuronal differentiation. Our findings indicate that the optimal concentration and duration of hypoxic preconditioning for promoting proliferation and differentiation of neural stem cells from the cerebral cortex are 5% oxygen for 72 hours.